There is only basilicin synthetase that is known to produce dipeptide by peptide bond forming activity at an α-carboxyl group of L-amino acid, which is a synthetic enzyme of a dipeptide antibiotic derived from a microorganism belonging to the genus Bacillus. Basilicin synthetase is known to have activity of synthesizing basilicin (L-alanyl-L-anticapsin, L-Ala-L-anticapsin) and L-alanyl-L-alanine (L-Ala-L-Ala) (see J. Ind. Microbiol., 2, 201-208 (1987) and Enzyme. Microbial. Technol., 29, 400-406 (2001)). It has been recently reported that this enzyme has activity of forming various dipeptides from the same or different free amino acids in various combinations (see WO 2004/058960).
However, the productive efficiency of some dipeptides is insufficient because of the substrate specificity of the above enzyme. Hence, a new dipeptide synthetase having substrate specificity differing from that of the above enzyme is required.
Bacillus subtilis ATCC6633 (“ATCC” is the American Type Culture Collection) is known to produce peptide antimicrobials, rhizocticin A (L-Arg-L-2-amino-5-phosphono-3-cis-pentenoic acid, L-Arg-L-APPA), rhizocticin B (L-Val-L-Arg-L-APPA), rhizocticin C (L-Ile-L-Arg-L-APPA), and rhizocticin D (L-Leu-L-Arg-L-APPA) (see Arch. Micromiol., 153, 276-281 (1990)). However, the biosynthetic pathway thereof, proteins involved in the biosynthesis thereof, and genes involved in the biosynthesis thereof remain unknown.